1. Field of the Invention
The invention relates to a method for generating TV signals and related apparatus, and more particularly, to a method for generating TV signals according to data lines similarities and related apparatus thereof.
2. Description of the Prior Art
The continuous and dynamic images of movies and television provided to viewers are in reality generated from a combination of gradually changing still images. When the television displays the video, there are two types of systems that have evolved to produce the continuous and dynamic flow of images. The first one is the national television standard committee (NTSC) system. In this system each video field includes 525 rows of data (i.e., 525 horizontal lines) and 60 pictures are displayed each second, i.e. the field rate is 60 Hz. The second system is called the phase alternating line (PAL), wherein each video field includes 625 rows of data and 50 pictures are displayed each second, i.e. the field rate is 50 Hz. For these two traditional television systems, to display 60 fields per second comprising 525 rows of data or to display 50 fields per second comprising 625 rows of data is extremely expensive, thus not suitable to the market. So, interlaced scanning technology was developed. Interlaced scanning scans the even lines for the first video field, then scans the odd lines for the next video field instead of scanning all lines for each field. Hence, for NTSC system with 60 Hz field rate actually 30 frames per second are processed, and for PAL system actually 25 frames per second are processed. However, the flow of dynamic images is still acceptable to the human eye. The images are still perceived as continuous and dynamic. Each frame in the interlaced scanning technology is divided into two parts: odd sequence data that is known as odd field and even sequence data that is known as even field.
However, a movie is displayed at a frame rate of 24 Hz. For NTSC system, as an example, when it is desirable to broadcast the movie to the television the movie's image data must be converted from its normal frequency of 24 Hz to 60 Hz.
Please refer to FIG. 1, which shows a comparison of the original film frames and interlaced TV fields. The upper part of FIG. 1 shows the original film frames A, B, C, and D, and the lower part of FIG. 1 shows 10 interlaced TV fields F1-F10 generated from the original film frames A, B, C, and D. For example, the odd lines of the film frame A associates with the TV fields F1 and F3. Furthermore, the even lines of the film frame A associates with the TV field F2, wherein Ao and Ae represent the odd field and the even field generated from the film frame A, respectively. Similarly, Be and Bo represent the even field and odd field from the film frame B. Ce and Co represent the even field and odd field from the film frame C. De and Do represent the even field and odd field from the film frame D. So, the frame rate of the film is 24 Hz, but the field rate of the NTSC system is 60 Hz. In other words, two film frames are transformed into five TV fields, so-called three to two pull down conversion, to comply with the NTSC system. Therefore, the total data amount is halved and the odd and even fields are displayed in the interlaced way.
Progressive scan is developed later and becomes popular, such as the LCD display or plasma TV. In progressive scan, the whole data lines, instead of only half data lines, of each video field are displayed. Therefore, when the progressive scan (or the double-frequency TV image technique) is utilized to display the field, which only comprise half data, fields should be transformed into frames, which comprise the whole data, so that the progressive scan can be executed correctly. The above-mentioned operation of transforming fields into frames is also called as “de-interlacing” technique. Generally speaking, two odd (even) fields corresponding to the same film frame are the same, but two odd (even) fields corresponding to two film frames are the same only if the two film frames are still. In the prior art, one field can be deinterlaced with the adjacent field to double the display resolution. However, if the original field data are the fields of film data as shown in FIG. 1, a serious problem occurs when the third field Ao and the fourth field Be are combined because the field Ao and the field Be correspond to different frames. Therefore, if the interlaced TV fields come from the film data, only the first pair of odd (even) fields is the same per five odd (even) fields.
Please refer to FIG. 2, which is a diagram of generating progressive TV frames. When we find that the fields F1 and F3 are the same and the fields F6 and F8 are the same, the source image data can be determined to be a film image. Therefore, the odd field F1 and the even field F2 can be combined as a progressive TV frame P1, which is labeled as A′. Similarly, the progressive TV frame P4, P6, and P9 are respectively labeled as B′, C′, and D′.
In the NTSC system, the frame rate of the progressive scan technique is 60 Hz. Therefore, the progressive TV frame P1 is utilized to generate the progressive TV frames P2 and P3. In other words, the progressive TV frame A′ is displayed in total three times. Similarly, the progressive TV frames P4 are copied to generate the progressive TV frame P5. That is, the progressive TV frame B′ is displayed twice. Similarly, the frame C′ is displayed three times, and the frame D′ is displayed twice.
When the TV data are broadcasted by the TV service provider, other data or information (for example, running text) is added to facilitate advertisements or news. Because of the introducing this additional data or information, two same fields looks different. If two same fields originates from the same film frame, the prior art may wrongly determine the mode of the TV content or wrongly processing the fields results in the running text becoming blurred.
In addition to adding the running text, other information can be added such that the original similarity pattern is influenced. For example, a still text or trademark is added, or the current time text can be added in the corner of the picture. These may cause a misinterpretation of the type of the source image. Please refer to FIG. 3, which shows a TV field sequence comprising still texts during a time period. As shown in FIG. 3, the fields F11-F20 are generated from film frames E, F, G, and H. The TV service provider adds a still text (e.g., a trademark of the TV service provider) in the fields F12-F17. Therefore, interlaced TV fields F11-F20 can be orderly shown as Eo, Ee′, Eo′, Fe′, Fo′, Ge′, Go′, Ge′, Ho, He, wherein the label′ represents that the field comprises the above-mentioned still text. Most TV service providers do not notice the 3:2 pull-down ratio relationships between the film frames and the interlaced TV fields while adding additional text, A sudden text shadow between the successive even and odd fields on TV screen may occur (e.g., between the fields Eo and Ee′ and between the fields Go and Ge′, where the still text is only added in one field of two successive fields). This cause the wrong determination of the mode of the TV content. If the fields are processed, the added texted area of the image becomes blurred. Alternatively, if we do nothing, the image quality becomes poor.